firm (adj.) Look up firm at Dictionary.com
late 14c., from Old French ferm (12c.) "firm, strong, vigorous, steadfast; loyal, faithful," from Latin firmus "firm, strong, steadfast, enduring, stable," from PIE root *dher- (1) "to hold, support" (cognates: Sanskrit dharmah "custom, law," Greek thronos "seat," Lithuanian dirzmas "strong," Welsh dir "hard," Breton dir "steel"). The return in late 1500s to -i- from Middle English ferme was modeled on Latin. Related: Firmly; firmness.
firm (n.) Look up firm at Dictionary.com
"business house," 1744, from German Firma "a business, name of a business," originally "signature," from Italian firma "signature," from firmare "to sign," from Latin firmare "make firm, affirm," in Late Latin, "confirm (by signature)," from firmus "firm, stable" (see firm (adj.)).
firm (v.) Look up firm at Dictionary.com
c.1300, fermen "make firm, establish," from Old French fermer (12c.) or directly from Latin firmare, from firmus (see firm (adj.)). Related: Firmed; firming.